Introduction: A 31-year old man was admitted in our emergency department for palpitation. A 12-lead electrocardiogram (EKG) showed a well tolerated regular narrow-QRS tachycardia. A bolus of 6mg + 12 mg of adenosine was administered with only temporary resolution of arrhythmia; subsequently an electric cardioversion was performed with restoration of sinus rhythm. A baseline EKG showed no sign of pre-excitation.
Electrophysiological study: A decapolar magnetic sensor-based catheter integrated with the electroanatomical mapping system was inserted through the right femoral vein and advanced in the right atrium (RA) where geometry reconstruction of this chamber was obtained (Figure 1). The catheter was easily advanced in the coronary sinus that appeared dilatated but failed to progress in the right superior vena cava. A venography was performed and confirmed the diagnosis of persistence left superior vena cava (PLSVC) and absence of right superior vena cava.
Two quadripolar catheters were advanced and positioned respectively at His bundle (HIS) and in the right ventricular apex (RVA).
During pacing from right ventricular (RV) apex an eccentric retrograde atrial activation was shown. After isoprenaline infusion during atrial programmed stimulation an atrioventricular reentry tachycardia was induced.
An intracardiac ecocardiography (ICE) connected with CARTO3 was positioned in the RA.
Atrial septal puncture was performed with ICE guidance and an 8.5F sheet was advanced in left atrium. Activation mapping during pacing from RVA showed maximum VA fusion at the postero-lateral localization. An open-irrigate contact force catheter (Smartouch SF; Biosense Webster, Inc., Irvine, California, USA) was inserted; multiple radiofrequency application with 30-35W were applied with resolution of the accessory pathway (Figure 2).
Conclusion: PLSVC is the most frequent congenital abnormality of the thoracic venous system. The prevalence of this condition is variable and range between a 0.2% and a 3% in the general population. This condition is generally asymptomatic and is accidentally found during procedure. In up to 90% of the cases, the right superior vena cava (RSVC) accompanies PLSVC. In a minority of cases RSVC failed to developed resulting in isolated PLSV.
The identification of PLSVC and the absence of RSVC during electrophysical study is crucial. For the purpose of a correct and safe transeptal puncture the use of intracardiac ultrasound is mandatory.
